Methods of the type mentioned at the outset are known from the related art. For the operation of hydraulic braking devices, it is known, especially in the case of motor vehicles, to recognize an emergency situation as a function of a driver's braking command and to set a brake boost to assist the driver in the emergency situation. Thus, it is known, for example, from DE 10 2010 002 574 A1 to recognize an emergency braking situation as a function of the driver's braking command and a change of the rotational speed of at least one wheel of the vehicle. Modern braking devices operate hydraulically, the driver of the motor vehicle being able to set a desired braking pressure via brake pedal actuation. Typically, the hydraulic pressure set by the brake pedal actuation acts on a brake master cylinder, which presses brake fluid into a conduit system of the braking device, the thus-generated pressure being available to the wheel braking devices for the application of a braking torque. It is known to provide braking devices of this type with a pneumatic brake booster that makes available a higher braking pressure at the same operating force of the brake pedal. Typically, the braking force is boosted by a vacuum. The vacuum may be provided, for example, by the vacuum present in the intake manifold of an internal combustion engine of the motor vehicle or by a separate vacuum pump. A typical pneumatic brake booster includes a prechamber and a main chamber, the vacuum being applied to both. The two chambers are normally separated by a displaceable diaphragm. More or less atmospheric pressure comes into the prechamber by actuation of the brake pedal, thereby supporting the brake pedal actuation.
It is also known to provide a hydraulic brake booster that generates additional braking pressure and actively assists the conventional vacuum brake boost if the conventional vacuum-controlled brake booster is no longer sufficient to produce the needed or desired braking force or to reduce the structural volume of the pneumatic brake booster. Braking devices of this type are known in particular in connection with ESP systems (ESP=electronic stability program), which stabilize the driving state of a motor vehicle by individual wheel brake interventions.
According to the aforementioned document, the triggering instant for the hydraulic brake boost is hitherto selected as a function of the vehicle behavior, in particular as a function of the wheel speeds. As a result, the hydraulic brake boost usually occurs in a time-delayed manner.